Comparison of Cerebral Autoregulation in Patients with Mild and Severe Arterial Hypertension

Abstract

Autoregulation of cerebral circulation (CA) is a mechanism at arteriolar level that ensures a constant cerebral blood flow (CBF) during changes in arterial blood pressure (ABP). Systemic arterial hypertension (SAH) is the leading cause of morbidity and mortality in the population worldwide, and may lead to structural and functional changes in the arteriolar wall resulting in an impairment of CBF regulation. While some studies have demonstrated that CA is retained in hypertensive patients, further associations with respect to SAH severity are limited. Therefore, this study aimed to evaluate CA response in SAH patients of differing severity. The data were collected from 15 participants with mild and 15 with severe hypertension. CA was assessed using four methods: autoregulation index (ARI), auto regressive moving average autoregulation index (ARMA-ARI), transfer function analysis (TFA) and mean flow index (Mx method). The results between SAH groups were compared through a statistical t test, and Spearman’s correlation was used to analyze the CA methods results. Results: No statistical difference was observed between mild and severe SAH groups. In the inter-method analysis, ARMA-ARI and Mx presented moderate correlation with ARI (p-values < 0.001, rho_ARMA-ARI = 0.44 and rho_Mx = −0.4). TFA presented weak correlation with ARI in the measures of LF range (p-values < 0.03, rho_{Coherence LF} = 0.28, rho_{Gain LF} = 0.28 and rho_{Phase LF} = 0.33). Conclusion: Sustained arterial hypertension does not alter CA within the ABP limits studied and the reproducibility of CA methods is poor to moderate when all SAH cases were used for the analysis.